Scientists engineered a new CRISPR platform for targeting DNA



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A team including scientists who first used revolutionary CRISPR-Cas9 and other systems for editing the genomes of eukaryotic organisms, including animals and plants, have engineered another CRISPR system, called Cas12b. This new system offers better capabilities and options compared to the CRISPR-Cas9 system.

In a study published today at Nature Communication, Feng Zhang and colleagues at the Broad Institute of MIT and Harvard and McGovern Institute for Brain Research at MIT, with co-authors Eugene Koonin at the National Institutes of Health, show that new enzymes can be engineered to precisely target the genomes of human cells . Specificity of target height and small size of Cas12b from Bacillus hisashii (BhCas12b) compared to Cas9 (SpCas9), making this new system suitable for in vivo applications. The team is now making CRISPR-Cas12b widely available for research.

The team previously identified Cas12b (later known as C2c1) as one of the three promising new CRISPR enzymes in 2015, but faced obstacles: Because Cas12b comes from thermophilic bacteria – which live in hot environments such as geysers, hot springs, volcanoes and deep-sea hydrothermal vents – enzymes only naturally work at temperatures higher than human body temperature .

"We are looking for inspiration from nature," Zhang said. "We want to make a Cas12b version that can operate at lower temperatures, so we scan thousands of genetic sequences of bacteria, looking for bacteria that can develop at lower temperatures than mammalian environments."

Through a combination of promising exploration of natural diversity and rational engineering candidate enzymes, they produced the Cas12b version that is capable of efficiently editing the genome in primary human T cells, an important first step for therapy that targets or utilizes the immune system.

"This is further evidence that there are many useful CRISPR systems waiting to be discovered," said Jonathan Strecker, a postdoc at Zhang Lab, a fellow Human Frontiers Science program, and the first author of the study.

This field moves fast: Because the Cas12b enzyme family was first described in 2015 and demonstrated as RNA-guided DNA endonucleases, several groups have explored the family of this enzyme. In 2017, the team from the Jennifer Doudna lab at the University of California at Berkeley reported from Cas12b Alicyclobacillus acidoterrestris can mediate the division of nonspecific collateral DNA in vitro. Recently, a team from the Chinese Academy of Sciences in Beijing reported that another Cas12b, from Alicyclobacillus acidiphilus, used to edit mammalian cells.

The Broad Institute and MIT share the Cas12b system extensively. As with previous genome editing tools, these groups will make technology freely available for academic research via Zhang's laboratory page on the plasmid sharing site, Addgene, where Zhang's lab has shared reagents more than 52,000 times with researchers in nearly 2,400 labs in 62 countries to accelerate research.

Zhang is a member of the core institute of the Broad Institute MIT and Harvard, and a researcher at McGovern Institute for Brain Research at MIT, James and Patricia Poitras Professor of Neuroscience at MIT, and professor at MIT, with combined appointments in the departments of Brain and Cognitive Sciences and Biological Engineering .

Support for this study was provided by the National Human Genome Research Institute, the National Institute of Mental Health, National Heart, Lung, and Blood Institute, and other sources. Feng Zhang is an investigator at the Howard Hughes Medical Institute.

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